Background:

The evaluation of the activity of the enzyme glutathione peroxidase (GSH-Px) as an indicator of selenium levels (Se) has been extensively studied with varying results between studies. The objective of this article was to determine the effect of Se supplementation on the activity of GSH-Px measured in blood serum and the possible impact of other dietary nutrients and experimental design elements on the response variable.

Methods:

The meta-analysis technique was used under the random effects model that included effect size, heterogeneity, metaregression and publication bias.

Results:

Dietary selenium supplementation increases (P < 0.00001) the enzymatic activity in general analysis (0.326 Units.mL-1) as when the supplemented sources were inorganic (0.327 Units.mL-1), organic (0.325 Units.mL-1), in piglets (0,261 Units.mL-1) and pigs in growth-completion (0,328 Unida-des.mL-1). The effect of supplementation on enzyme activity was not presented consistently among studies as reflected in the values in the inconsistency test (> 95 %). In the meta-regressions it was determined that the activity of GSH-Px is affected (P < 0.001) by number of repetitions per treatment, number of individuals per experimental unit, number of individuals sampled per experimental unit, selenium level, copper, zinc, vitamins A and E in food.

Conclusions:

From this research it is concluded that the dietary supplementation of the GSH-Px activity measured in serum is favored and that there are several factors related to the experimental design and other nutrients with antioxidant function that affect the variable under study.